Bug 1305957 part 9 - Suppress scroll offset adjustment when node moves into flow or out of flow inside of a scrollable frame. r=emilio
This commit implements the second half of the heuristics to detect style changes
that could lead to feedback loops with scroll anchoring. [1]
A new change hint is added for when a style is changed from positioned to not
positioned. When this hint is applied, scroll anchor suppression is triggered in
the scroll anchor container where the frame used to be, and the new scroll
anchor container where the frame is added after reconstruction.
[1] https://drafts.csswg.org/css-scroll-anchoring/#suppression-triggers
Differential Revision: https://phabricator.services.mozilla.com/D13273